The invention offers a solution for the need for motor-gear drive units that require a large reduction (larger than 1:5) in a very compact and robust design. It is furthermore very suitable to be supported from one side. In certain applications of these motorized drive units, size restrictions are imposed by a demand for maneuverability and user friendliness. A good example of such an application is an indoors patient lift vehicle with steerable motorized traction wheels (FIG. 6). The motorized wheels must be very compact to allow for good operability in small interior spaces. The wheels should preferably be suspended from a single side to achieve more compactness. To be able to travel at slow speeds, the integrated drive reduction must be large enough to deliver a high output torque at a low rotational wheel speed. The invention aims at a more compact and robust design than the conventional motor-gear drives, which use for example a reduction mechanism with worm gears, multi-stage planetary gears or even cycloidal gears. Worm gears can achieve large reductions, but have as main disadvantages the large size, high friction and high demands on manufacturing tolerances.
Known motor-gear drive units predominantly use a planetary gear reduction, see for example CN102673380. A single stage planetary gear set is suitable for reductions as large as 1:5. To achieve larger reductions, multiple stages of planetary gear sets are used. However, this increases the size of the unit and increases the component count and manufacturing costs.
Cycloidal gear reduction, which is able to achieve larger reduction ratios than a planetary gear set is known. The following publications give an overview of the working and design principles of cycloidal gear reductions:                Design and application guidelines for cycloid drives with machining tolerances, D. C. H. Yang, J. G. Blanche, Mech. Mach. Theory Vol. 25, No. 5, pp. 487-501. 1990, Pergamon Press        Design of a Planetary-Cyclo-Drive Speed Reducer: Cycloid Stage, Geometry, Element Analyses. B. Borislavov, I. Borisov & V. Panchev, 2012, Linnaeus University        
A known motor-gear drive unit which uses a cycloidal gear reduction is U.S. Pat. No. 8,506,438 B2, this and other similar motor-gear drive units operate with two meshing gear profiles wherein one of the meshing gear profiles comprises rollers and make use of the carrier/guide pins as the power output.
The available constructions fail to meet the needs for a compact design, a reduced axial width, a reduced component count, being suitable for mounting on a single side, and a high reduction ratio.